NVIDIA Mellanox MCX4121A-ACAT ConnectX-4 Lx EN 25GbE Dual-Port SFP28 PCIe 3.0 x8 Network Adapter: This is a dual-port 25GbE Ethernet Network Interface Card (NIC) based on the ConnectX-4 Lx controller, with two SFP28 cages and a PCIe Gen3 x8 host interface. It is shipped with a tall (full-height) bracket. This is an Ethernet-only adapter — it is NOT a VPI adapter and does not run InfiniBand. This is a refurbished unit, tested by T.E.S IT-SOLUTIONS.
Engineering Context
The ConnectX-4 Lx silicon delivers up to 25Gb/s per port using NRZ encoding over SFP28. PCIe Gen3 x8 provides up to 64 Gb/s of raw host bandwidth, sufficient to sustain both ports at line rate for typical workloads. The adapter implements stateless TCP/IP/UDP offloads, RDMA over Converged Ethernet (RoCE v1 and v2), SR-IOV, and overlay tunnel offloads (VXLAN, NVGRE, Geneve), reducing CPU overhead on the host. The Lx variant is positioned as the cost- and power-optimized 25GbE option in the ConnectX-4 family.
Deployment & Use Cases
Hyperconverged infrastructure (vSAN, Nutanix, Azure Stack HCI) requiring 25GbE east-west fabric. KVM/VMware hosts needing SR-IOV-capable 25GbE NICs. Ceph and other software-defined storage clusters. NFV and telco edge nodes. RoCE-enabled storage targets where NVMe-oF performance is required without 100GbE-class power draw.
Technical Specifications
OEM: NVIDIA Mellanox
Part Number: MCX4121A-ACAT
Controller: ConnectX-4 Lx EN
Ports: 2 × SFP28
Data Rate: 25GbE per port (also 1/10GbE)
Host Interface: PCI Express Gen 3.0 x8
Protocol: Ethernet only (not VPI)
Bracket: Tall (Full-Height)
Offloads: RoCE v1/v2, SR-IOV, VXLAN/NVGRE/Geneve, TCP/IP stateless
Form Factor: Low-profile half-length PCIe card
Condition: Refurbished — Tested by T.E.S IT-SOLUTIONS
Compatibility & Hard Constraints
Compatible with mainstream x86 servers (Dell PowerEdge, HPE ProLiant, Supermicro, Lenovo ThinkSystem) that expose a PCIe 3.0 x8 (or wider) slot. Inbox drivers are included in modern Linux distributions and Windows Server. Requires SFP28 transceivers or DAC/AOC cables for the link. Does NOT support InfiniBand — for VPI capability use a ConnectX-4 VPI part (e.g., MCX455/MCX456 series). Does NOT include a low-profile bracket in this configuration.
Why Choose T.E.S IT-SOLUTIONS
Every adapter is bench-tested for both ports, link training, and PCIe enumeration before shipment. T.E.S IT-SOLUTIONS ships globally with 1–3 business day handling and provides architectural guidance on 25GbE rollouts.